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A Brief History of the Real-Life Invisibility Cloak

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By Chris Gayomali

The evolution of the cloaking device, from its origins in Star Trek fantasy to intricate new metamaterials.

March 27, 1958

Run Silent, Run Deep, a World War II naval drama starring Clark Gable and Burt Lancaster, reportedly inspires Star Trek screenwriter Paul Schneider to mull a space-exploration equivalent to a submarine submerging underwater. What to do...

Dec. 15, 1966

Invisibility technology makes its Star Trek debut in episode 14, "Balance of Terror," when a Romulan Bird of Prey equipped with a cloaking device attacks the Starship Enterprise.

Sept. 27, 1968

In episode 59, "The Enterprise Incident," the technology finally gets a name: It's called a "cloaking device." The Trekkie trope inevitably becomes a sci-fi staple, appearing (and disappearing?) in everything from Dr. Who to Predator to Stargate.

June 26, 1997 

A divorced mother of a young child quietly publishes a children's book about a young orphan who receives an invisibility cloak as a Christmas present. Only 1,000 copies of Harry Potter and the Philosopher's Stone are printed.

Oct. 2006

Physicists from Duke University unveil the world's first-ever invisibility cloak. (Thanks, J.K. Rowling!) The elaborate set-up was created using metamaterials, which are capable of manipulating wavelengths — like light — in ways that aren't found in nature. The catch? This "cloak" only works on microwaves and in two dimensions.

Oct. 2007

The British military tests something frightening: An invisible tank, which uses cameras and projectors to beam the surrounding landscape onto the vehicle's hull. Says one soldier who was apparently at the test trials: "This technology is incredible. If I hadn't been present I wouldn't have believed it. I looked across the fields and just saw grass and trees — but in reality I was staring down the barrel of a tank gun."

Summer 2008

Scientists at the University of California, Berkeley, use metamaterials to change the natural direction of visible and near-infrared light in three dimensions. Developed by Xiang Zhang, a professor at Berkeley's Nanoscope Science and Engineering Center, the light-bending concept is likened to viewing a distorted straw through a glass of water.

Summer 2008

The U.S. Army expresses interest in using metamaterials to cloak its vehicles, soldiers, and other weapons, thereby allowing them to bypass radar and sensors. Dr. Richard Hammond at the Army Research Office thinks the military is about two or three years away from manufacturing actual cloaking devices. 

May 2009

U.C. Berkeley's Zhang engineers a "carpet cloak" from nanostructured silicon that successfully hides small objects from the near-infrared portion of the electromagnetic spectrum. Zhang says the cloak "should be upwardly scalable," meaning that, in theory, it could work in the visible spectrum to distort objects from view.

March 2009

Across the Atlantic, military interest in cloaking devices continues to build. This time, a lecturer at the British Royal Navy College considers "the next generation of stealth ships that could be virtually invisible to the naked eye, roaming radars, and heat-seeking missiles," says Gizmag

Aug. 2010

Scientists at Tufts and Boston universities create a tiny invisibility cloak capable of manipulating terahertz waves. One problem: This new class of metamaterial was crafted by etching 10,000 gold resonators onto a 1 cm square of silk. Luxury! 

Dec. 2010

Nature reports that two scientists — one based in Singapore, one based in London — develop a more effective metamaterial from calcite crystals, which are much cheaper than, well, gold-etched silk.

Oct. 2011

Now we have video! University of Texas researchers demo a real-life invisibility cloak that uses carbon nanotubes. 

March 5, 2012

Mercedes debuts an "invisible car" as part of a promotional stunt. Okay, it's not really invisible, but the vehicle uses cameras and moving images the same way that the British tank mentioned above does.

November 2012

Researchers from Duke University create a "flawless" invisibility cloak capable of completely hiding tiny objects, in this case a 7.5 by 1 cm cylinder. So what constitutes a flawless cloak? This one channels incident light completely around an object. Voilà — pristine, perfect invisibility.

March 2013

The biggest problem with all the aforementioned cloaking devices is that they're big, bulky, and cumbersome. They need lab desks to work. But not for much longer: University of Texas, Austin researchers have created an ultra-thin material that's just 0.15 mm thick. Now, says Sebastian Anthony at ExtremeTech, "it's really only a matter of time until an actual invisibility cloak is realized."

Sources: ABC NewsU.C. BerkeleyThe Daily MailExtreme TechGizmagThe GuardianThe Huffington PostNational GeographicPrinceton UniversityScience DailyWired

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technology
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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Scientists Think They Know How Whales Got So Big
May 24, 2017
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It can be difficult to understand how enormous the blue whale—the largest animal to ever exist—really is. The mammal can measure up to 105 feet long, have a tongue that can weigh as much as an elephant, and have a massive, golf cart–sized heart powering a 200-ton frame. But while the blue whale might currently be the Andre the Giant of the sea, it wasn’t always so imposing.

For the majority of the 30 million years that baleen whales (the blue whale is one) have occupied the Earth, the mammals usually topped off at roughly 30 feet in length. It wasn’t until about 3 million years ago that the clade of whales experienced an evolutionary growth spurt, tripling in size. And scientists haven’t had any concrete idea why, Wired reports.

A study published in the journal Proceedings of the Royal Society B might help change that. Researchers examined fossil records and studied phylogenetic models (evolutionary relationships) among baleen whales, and found some evidence that climate change may have been the catalyst for turning the large animals into behemoths.

As the ice ages wore on and oceans were receiving nutrient-rich runoff, the whales encountered an increasing number of krill—the small, shrimp-like creatures that provided a food source—resulting from upwelling waters. The more they ate, the more they grew, and their bodies adapted over time. Their mouths grew larger and their fat stores increased, helping them to fuel longer migrations to additional food-enriched areas. Today blue whales eat up to four tons of krill every day.

If climate change set the ancestors of the blue whale on the path to its enormous size today, the study invites the question of what it might do to them in the future. Changes in ocean currents or temperature could alter the amount of available nutrients to whales, cutting off their food supply. With demand for whale oil in the 1900s having already dented their numbers, scientists are hoping that further shifts in their oceanic ecosystem won’t relegate them to history.

[h/t Wired]

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